1,2-Dibromoethane → (2R,3S,5S)-5-((1S,3S)-3-Benzyloxymethyl-1-hydroxy-4-methyl-pentyl)-3-isopropyl-2-[4-methoxy-3-(3 methoxy-propoxy)-phenyl]pyrrolidine-1-carboxylic acid tert-butyl ester

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Reaction Steps

A solution of 1.98 g of aldehyde 7 in 15 mL of tetrahydrofuran is cooled to 10° C. and is treated with the Grignard reagent prepared by treating 1.23 g of ((S)-2-bromomethyl-3-methylbutoxymethyl)-benzene with 0.12 g of magnesium in diethylether containing 0.043 g of 1,2-dibromoethane at 45° C. The reaction is stirred for 90 minutes at room temperature, then 20 mL of a 25% aqueous solution of ammonium chloride is added, followed by addition of 20 mL of tert-butylmethyl ether. The organic phase is separated and washed twice with 20 mL of water. The organic phase is concentrated in vacuum to give the crude alcohol 8 as an oil. Purification on silica-gel delivers e.g. 0.97 g of pure 8. A negative [a]d is found at c=1, CHCl3. M++H=628, M++H+Na=650.

Provenance & Evidence